Which of the following study designs is considered an experimental study?

Experimental studies involve the investigator actively intervening and assigning participants to groups (experimental vs. control), with randomization to reduce bias. A randomized clinical trial (RCT) is the gold standard experimental study design. Surveys, case-control studies, and cross-sectional studies are all observational (non-experimental) designs — the investigator merely observes without intervention. Cohort studies can be prospective observational studies but are not experimental unless there is an intervention.